Biggest Axle in stock rear end housing

[67aj]

I have a 73 mustang that has 28 spline axle and planning on up grade for more horse power what is the biggest spline axle that i can install in the housing i have i know i have to change the differential to match thank

 

[Tnfastbk]

most go with 31 spline axles for an upgrade, The 28 hold up quite well though unless you are making stupid HP.

 

[Cleveland Crush]

How much power you planing on, along with
gear ratio, type of tires (slicks, street tires) and intended use are big factors. For a straight forward no hassle swap in upgrade, this Moser 31 spline is one option. Most of the axle guys make a similar option.

 

[Cleveland Crush]

https://www.moserengineering.com/1971-73-mustang-ds-and-ps-spline-31.item

 

[67aj]

Going to be installing a big block with 800 too 900 horse power C6 transmission 389 rear gear this going to be a street and strip car

 

[Don C]

Because your differential housing is likely the small bearing version (axle bearings) you're pretty much limited to 31 spline off-the-shelf axles. The Moser axles will be stronger than the original Ford axles, I believe they use a stronger alloy. Moser may be able to custom build you a small bearing 33 or 35 spline axle. A 40-spline axle may require a different housing.

 

[Cleveland Crush]

Going to be installing a big block with 800 too 900 horse power C6 transmission 389 rear gear this going to be a street and strip car

Consider an aftermarket/fabricated 9" Ford housing and center section to comfortably accommodate your stated parameters.

 

[c9zx]

Street/Strip means no spool, in my mind. So, perhaps a Detroit locker with 35 spline axles. I had a Versailles rear end with that set up, it worked fine with 575 HP. I don't know about 900 HP. You need to check axle bearing compatibility. Ford used small, old large, and new large bearing housings. My set up was from Strange Engineering. Good luck with the build. Chuck

 

[tony-muscle]

Depending on your budget, I agree with @Cleveland Crush to consider a fabricated housing with new beefy internals from the likes of Moser, Strange, etc, to handle that much power. I will go with a big bearing. With that kind of power your type of tire will dictate the amount of torque you can apply without spinning. With street tires you may be able to survive, but with slicks it would be a different story. Call them and see what they think.

 

[BUCKWHEAT]

Going to be installing a big block with 800 too 900 horse power C6 transmission 389 rear gear this going to be a street and strip car

With those target goals, I would suggest you are describing a 'street-legal race car".

 

[Hemikiller]

At that power level, you'll want to upgrade the housing and the carrier.

 

[mach72]

I would contact Quick Performance in Iowa. They can build you a custom housing at a very good price. They can build the entire rear end for you also. Very good prices too.

 

[stajp]

Because your differential housing is likely the small bearing version (axle bearings) you're pretty much limited to 31 spline off-the-shelf axles. The Moser axles will be stronger than the original Ford axles, I believe they use a stronger alloy. Moser may be able to custom build you a small bearing 33 or 35 spline axle. A 40-spline axle may require a different housing.

Yes.

 

[67aj]

Thanks to everyone for the information.

 

[Spike Morelli]

Call it what you may, but if it has a license plate on it, and you don't keep it on a trailer....it's a street car. Build accordingly.